At a glance
～も同然だ means "as good as ~", "practically ~" or "virtually ~". Use it when something is not officially or literally X but is so close that it can be treated as X.
[Noun] + も同然だ
[Verb plain form (usually た-form)] + も同然だ
この車は新品も同然だ。 This car is as good as new.
How to form it
| Attaches to | Form | Example | Meaning |
|---|---|---|---|
| Verb, た-form (most common) | 決まった + も同然だ | 決まったも同然だ | as good as decided |
| Verb, other plain forms | 知っている / ない + も同然だ | 知っているも同然だ | practically knows |
| Noun | 新品 + も同然だ | 新品も同然だ | as good as new |
For the polite form, change だ to です: 新品も同然です.